First off, I want you to breathe...
I know that is SO terribly annoying to hear. But the truth is deep, cleansing breaths can make everything more doable. It clears up your brain fog, gets oxygen to all your cells for more energy, more stamina, which you need even more of during times of stress and crises. Yet it is also the quickest and simplest way to relax. So breathe first, b/c I feel all your stress and it's sitting right on top of your chest like a ton of bricks. How can you get through anything feeling like that and not breathing?
Secondly, the first change I feel you need to initiate is within your marraige and with your children. I want you to start focusing on setting up some strong emotional boundries with your children. This is exactly what I'm hearing. So I'm not totally sure what that means, but I believe you will.
I also want you to work on remembering that you don't have to take abuse, b/c you are wanting change. It doesn't make you a bad person. You obviously already feel guilty. But I do sense that there will be a verbal backlash from your spouse that could take you down if you let it. So you need to get yourself emotionally in check before any confrontations. You need to learn to not take anything he says personally. You can choose to do this. It's not something you have to work hard at. Just simply don't take anything he says personally. He's going to say whatever he wants. It will be hurtful. So this is my warning to put up all protective walls around you. Put your "bubble of peace" around you.
I don't think you should wait any longer than you have to. Waiting is not making it better..you are just dragging out the enivitable.
I hope this helps you get some bearings. This is a really large question for this forum. I understand you want help and I want to help you. I suggest you get a full reading.
No matter what, remember to breathe. You will not get anything done well breathing all tight and high in your chest like you have been doing. Take the breath down all the way to the gut.